1. The Pacific Northwest’s Changing Hydrology
Marketa McGuire Elsner
University of Washington
JISAO/CSES Climate Impacts Group
Dept of Civil and Environmental Engineering
February 12, 2008
Climate Change Effects to Fish and Wildlife Resources – FWS Training
Climate science in the public interest

2. Recession of South Cascade Glacier
Upper Skagit River Basin, Washington
The U.S. Geological Survey (USGS) operates a long-term "benchmark" glacier program to monitor climate, glacier geometry, glacier mass balance, glacier motion, and stream runoff. South Cascade Glacier is one of these.
Source: U.S. Geological Survey

3. Cool Season Climate of the Western U.S.
PNW GB CA
CRB
Cool season temperatures – in the PNW much of our cool season temperatures hover near freezing. Therefore, small changes in average temperatures have the potential for large impacts in this region which is hydrologically dominated by snowmelt.
Cool season precip – much of our cool season precip falls on the west side of the cascade mountains and in the mountains themselves. Therefore, mountain snowpack plays a large role in the soil moisture and hydrology of the arid parts of the region. Changes in snowpack and temperatures have the potential for a large impact in this region.
DJF Temp (°C)
NDJFM Precip (mm)

4. Understanding
Climate Variability

5. Observed 20th century variability
(~5.5°F)
+3.2°C °C
(~3.1°F)
(~1.2°F)
+1.7°C
+0.7°C °C °C
Observed 20th century variability
Curves are fits to ln(CO2) for A2 (solid) and B1 (dashed)
Warming ranges are shown for 2020s, 2040s and 2090s relative to 1990s. Central estimates: 0.7C by 2020s, 1.7C by 2040s, 3.2C by 2090s. Pink box shows +/- 2 sigma for annual average temperature (sigma=0.6C). Red lines show previous generation of change scenarios. °C
Pacific Northwest

6. Observed 20th century variability%
-1 to +3%
+6%
+2%
+1%
Curves are fits to ln(CO2) for A2 (solid) and B1 (dashed)
Precip changes are shown for 2020s, 2040s and 2090s relative to 1990s. Central estimates: 1% by 2020s, 3% by 2040s, 6% by 2090s. Pink bar shows +/- 2 sigma for PNW annual precip.
Observed 20th century variability
-1 to +9%
-2 to +21%
Pacific Northwest

7. Regionally Averaged Temperature Trends Over the Western U.S. 1916-2003
Tmax
PNW GB
Tmin CA
CRB
Figure 4

8. Regionally Averaged Cool Season Precipitation Anomalies

9. Global Climate Change Scenarios and Hydrologic Impacts for the PNW

10. 824 snow courses 73% – trends Large – trends PNW Some + trends SW
Trend in Apr 1 Snowpack
824 snow courses 73% – trends Large – trends PNW Some + trends SW
Figure source: Climate Impacts Group 10

11. The warmer locations are most sensitive to warming
+6.8% winter precip

12. Planning Framework to Incorporate Climate Information and Uncertainty
Approach provides ensemble of variables that can be used to evaluate impacts of climate change
Emissions
Scenarios
GCMs
Downscaling X X
Climate Scenarios
Precipitation
Air Temperature
Streamflow
Soil Moisture
PET
VPD
And more!
Overall Process for HB1303 Project:
Generally, a range of scenarios of climate change to 2100 are input to a hydrology model that provides projections of streamflow and other hydrologic variables.
-We are utilizing 100 year projections from approximately 20 GCMs, each of which has projections using 2 emissions scenarios. These emissions scenarios, A1B and B1, represent stabilization of CO2 by The B1 scenario is more ecologically friendly than A1B. They generally represent the range of possibly temperature changes into the future.
-The GCM scenarios, which are at a resolution of approximately 3-4 degrees, must be downscaled to the resolution of the hydrology model. We utilize 2 downscaling approaches including a statistical approach and an approach that incorporates results from regional climate models.
The downscaled GCM predictions and resulting hydrologic predictions provide a range of possibilities of future climate change which the various sectors can use to evaluate the impacts in their areas.
Hydrology Modeling

13. Hydrology and Water Resources -Snowpack
Snowpack will continue to decrease.
Declines in April 1 SWE vary between 35%-41% for the 2040s, depending on the emissions scenario.
There are 40 total greenhouse gas emissions scenarios used to drive global climate models. The 40 scenarios are grouped into four families: A1, A2, B1, and B2. The CIG is using the B1 and A1B scenarios for the HB 1303 work.
The B1 emissions scenario represents a slower increase in greenhouse gas emissions with stabilization of CO2 concentrations by 2100 (the concentration of carbon dioxide will be 550ppm in 2100). The A1B emissions scenario has higher greenhouse gas emissions than the B1 scenario: the concentration of carbon dioxide will be 720ppm in 2100.
The A1B and B1 scenarios have the same population projections (population peaking mid-century then declining). The main difference in the scenarios is energy use. The A1B scenario story line has a balance between fossil fuels and other energy sources, while the B1 story line assumes the use of more clean and resource-efficient technologies. 13

14. Hydrology and Water Resources -Projected Changes in Soil Moisture
Changes in soil moisture will be mixed.
Declines may be expected in the 2040s in mid-elevation areas, while increases may be expected in highest elevation areas.

15. Simulated Changes in Natural Runoff Timing in the Naches River Basin Associated with 2 C Warming
Impacts:
Increased winter flow
Earlier and reduced peak flows
Reduced summer flow volume
Reduced late summer low flow

16. Chehalis River

17. Hoh River

18. Nooksack
River

19. HUC 4 Scale Watersheds in the PNW
Mapping of Sensitive Areas in the PNW by Fraction of Precipitation Stored as Peak Snowpack
HUC 4 Scale Watersheds in the PNW

20. Climate Change Impacts are Similar to
Impacts of Water Management in PNW Hydropower Systems
Estimated natural flows
Skagit River at Mt. Vernon

21. Summary of Flooding Impacts
Rain Dominant Basins:
Possible increases in flooding due to increased precipitation variability, but no significant change from warming alone.
Mixed Rain and Snow Basins Along the Coast:
Strong increases due to warming and increased precipitation variability (both effects increase flood risk)
Inland Snowmelt Dominant Basins:
Relatively small overall changes because effects of warming (decreased risks) and increased precipitation variability (increased risks) are in the opposite directions.

22. Landscape Scale
Ecosystem Impacts

23. Forests
Wildfires are strongly associated with climate, especially in eastside forests.
Mountain pine beetle poses a significant threat to PNW pine forests.
Tree species composition will change as species respond uniquely to a changing climate.
Productivity of Douglas-fir forests is likely to decrease statewide.
Supporting text (taken directly from the interim report):
1. Without an increase in summer precipitation (greater than any predicted by climate models), future area burned is very likely to increase. Forests east of the Cascade crest will be most susceptible to larger and more severe fires in a changing climate.
2. Although other insect populations may increase with warmer temperatures, the mountain pine beetle poses the greatest threat of damage to Washington forests over the next several decades because it responds directly to warmer temperatures. Eastside forests dominated by lodgepole pine and possibly ponderosa pine, both host species for the beetle, will be most susceptible in a changing climate.
3. Washington state forests most likely to experience major changes in composition in a changing climate will be those near the lower treeline on the east side (ponderosa pine and Douglas-fir) and at the upper treeline on both sides of the Cascade Crest.
4. The limiting factors for Douglas-fir growth may change from light availability (particularly westside lower elevations) and cold (upper elevations) to water-balance deficit over significant acreage in Washington. The most vulnerable part of the state will initially be montane Douglas-fir stands on the east side, but eventually the more productive commercial forests of the west side. 23

24. Annual area (ha × 106) affected by MPB in BC
9.0
2005
Bark Beetle Outbreak in British Columbia
8.0
7.0
2004
6.0
5.0
Annual area (ha × 106) affected by MPB in BC
2003
4.0
3.0
By last year, the total area of beetle-caused mortality spread over some 10 million hectares
2.0
2002
1.0
2001
2000
1999
1910
1930
1950
1970
1990
2010
(Figure courtesy Allen Carroll)
Year

25. Temperature thresholds for coldwater fish in freshwater
Warming temperatures will increasingly stress coldwater fish in the warmest parts of our region
A monthly average temperature of 68ºF (20ºC) has been used as an upper limit for resident cold water fish habitat, and is known to stress Pacific salmon during periods of freshwater migration, spawning, and rearing
+3.1 °F
+4.1 °F

26. Projected Maximum Weekly Average Water Temperatures – 2040s
Salmon
Water temperature is already a problem in many WA stream reaches.
Exceedences of WQ criteria for temp, especially in summer, will increase with warmer summer temperatures and reduced low flows due to earlier snowmelt.
Projected Maximum Weekly Average Water Temperatures – 2040s
From the interim report:
In the period, 15% of the stations included in our analysis had an observed maximum weekly average water temperature greater than the 21ºC (70°F) water quality criteria, and all of those stations are located in the interior Columbia Basin. Under the A1B emissions scenario, 2040s August average air temperatures are projected to rise by 2.8ºC (approximately 5.0°F). Using the delta method by assuming an equivalent rise in the annual maximum weekly water temperature results in 49% of these stations exceeding the 21ºC (70°F) criteria, with many recording stations in southwest Washington and the Puget Sound Lowlands and all the stations in the Columbia Basin exceeding the 21ºC (70°F) criteria. Although this approach ignores a range of factors that give rise to the observed heterogeneity in stream temperatures, this simple projection should give a useful preview of the projected stream temperatures we will develop in the next year using the 1/16 degree gridded air temperature fields and empirically-based stream temperature models.
The period of maximum temperatures will vary from stream to stream, therefore this figure is generally for summer temperatures and is not tied to a specific month (although most occurred in September). How were these values calculated? We took the average weekly maximum water temperature at each station for and averaged those max temps at each site. Changes are calculated from this base period.
49% of stations exceed the 21ºC (70°F) water quality criteria (changes relative to ) 26

27. Agriculture
Irrigation supplies are likely to decline significantly as a result of changes in snowpack, resulting in more frequent and more stringent prorationing of water to junior water rights holders.
For dryland agriculture, climate change will force agricultural practices to adapt to longer growing seasons, reduced summer precipitation, and increasingly competitive weeds.
Diseases will generally become more problematic over the next century, especially as a result of warmer temperatures.
The potential for adaptation will vary strongly by crop type.
These results are based on previous work to date and literature reviews. 27

28. Impact Pathways Associated with Climate
Changes in water quantity and timing
Reductions in summer flow and water supply
Increases in drought frequency and severity
Changes in hydrologic extremes
Changing flood risk (up or down)
Summer low flows
Changes in groundwater supplies
Changes in water quality
Increasing water temperature
Changes in sediment loading (up or down)
Changes in nutrient loadings (up or down)
Changes in land cover via disturbance
Forest fire
Insects
Disease
Invasive species

29. Impact Pathways Associated with Climate
Changes in water management practice
Hydropower production (energy demand)
Flood control operations (changing flood risk and refill statistics)
Instream flow augmentation
Use of storage to control water temperature
Changes in Ecosystem Protection and Recovery Planning
Design of fish and wildlife recovery plans
Habitat restoration efforts
ESA listings (as a process)
Monitoring programs

30. Approaches to Adaptation and Planning
Anticipate changes. Accept that the future climate will be substantially different than the past.
Use scenario based planning to evaluate options rather than the historic record.
Expect surprises and plan for flexibility and robustness in the face of uncertain changes rather than counting on one approach.
Plan for the long haul. Where possible, make adaptive responses and agreements “self tending” to avoid repetitive costs of intervention as impacts increase over time.

31. The Climate Impacts Group Marketa McGuire Elsner
More information on the Climate Impacts Group or WA State Climate Impacts Assessment
The Climate Impacts Group
Marketa McGuire Elsner
Climate science in the public interest

32. Motivation for writing grew out of October 2005 King County climate change conference
Written by the CIG and King County, WA in association with ICLEI – Local Governments for Sustainability
Focused on the process (not a sector), and written for a national audience 32

33. Hydrologic Scenarios Database for the Columbia River Basin
Working in Coordination With Regional Stakeholders
Ecology
BPA
NPCC
State of OR
British Columbia (BC Hydro, Ministry of Environment)
As the public and professionals in the water management and policy arenas have become increasing concerned about the impacts of climate change on PNW water resources, demand for hydrologic scenarios suitable for planning purposes at a range of spatial scales has increased dramatically.
Currently there does not exist an up-to-date, comprehensive, and self-consistent data base of hydrologic scenarios for the Columbia River basin that is suitable for the range of planning activities the Climate Impacts Group is being asked to support.
Planning Framework Incorporating Climate Information and Uncertainty
~20 GCMs
2 Emissions Scenarios
2 Downscaling Approaches
Large Scale Planning Studies
WRIA Water Supply Planning
Specific Planning Studies

34. Coasts 3” 6”
30”
50”
2050
2100
13”
40”
20”
10”
Rising sea levels will increase the risk of flooding, erosion, and habitat loss along coastline.
Medium estimates of SLR for 2100: +2” for the NW Olympic Peninsula +11” for the central/southern coast +13” for Puget Sound Higher estimates (up to 4 feet in Puget Sound) cannot be ruled out.
Episodic flooding will likely pose a greater risk than permanent inundation of low-lying areas from increases in mean sea level.
Lower amounts of local SLR will be apparent on the northwest Olympic Peninsula given rates of local tectonic uplift that currently exceed projected rates of global SLR. SLR estimates for the central and southern Washington coast are more uncertain. Available (but limited) data suggests that uplift is occurring in this region, but at rates lower than observed on the northwest Olympic Peninsula. The 6” and 13” marks on the figure are the SLR projections for the Puget Sound region and effectively also for the central and southern WA coast (the rates are nearly identical for the central and southern coast: +5 inches by 2050 and +11 inches by 2100)
Assumptions of continued rapid ice melt from Greenland and Antarctica are a major factor in the potential for higher amounts of SLR. 34